In the related art, in kneading machines for rubber manufacturing, such as a so-called internal mixer, heat is generated with kneading because the kneading is performed by applying a strong shear force to a material, such as rubber. When the temperature of rubber becomes excessive due to such heat generation, sufficient cooling capacity is required because the quality of rubber degrades. Also, when the cooling capacity is insufficient, it is necessary to perform the kneading again after rubber is discharged to the outside in the middle of the kneading and is cooled to decrease in temperature thereof. Therefore, productivity is greatly affected.
Here, an example of a kneading machine including a rotor for kneading with a so-called one-piece structure in which a rotor shaft and a blade part are integrally formed is described in PTL 1.
The kneading machine of PTL 1 accommodates a rotor for kneading having the rotor shaft provided with a cooling passage and the blade part for kneading, inside a mixing chamber thereof.
Additionally, in this kneading machine, a branch pipe is provided in an inner pipe accommodated in the cooling passage formed in the rotor shaft so that the cooling passage and a cavity portion (jacket) inside the blade part communicate with each other, and the cooling effect of the blade part is improved such that a cooling medium fed to the cooling passage is reliably introduced into the cavity portion inside the blade part.